It has been known that when an image is displayed on a display and a particular position on the image is pressed by a finger, X and Y coordinates of the pressed part become detected by a pressure-sensitive sensor and the like, and a next behavior is performed based on this input signal (see, e.g., Patent Literature 1).
Also, as described in Patent Literature 2, when forming a matrix by arranging, right above a display, a number of light-emitting elements along X-axis and in parallel with one another and a number of light-receiving elements along Y-axis and in parallel with one another, and touching the surface of the display with an obstacle such as a finger and a pen, it is proposed to detect a position having come into direct contact with the display by crossing of the obstacle on the matrix.
On the other hand, in Patent Literature 3, there is proposed a method and apparatus that detect an indicated position on a reproduced image by using a optical image formation means in which a first light control panel having a number of first planar light-reflective portions arranged in parallel with one another at constant intervals inside a transparent flat plate and a second light control panel having a number of second planar light-reflective portions arranged in parallel with one another at constant intervals inside a transparent flat plate are arranged in direct contact with or proximity to each other in a manner that makes the first planar light-reflective portions and the second planar light-reflective portions orthogonal in planar view, simultaneously displaying an image on a display and an image formed by making infrared light irregularly reflect off the surface of the display as reproduced images in the air, and detecting a position of an indicating means having touched the reproduced images by a two-dimensional infrared camera.
As described in Patent Literature 4, there is also a proposal of an apparatus that cognizes a form of movement of a multi-touch by means of fingers or a stylus pen on a liquid-crystal surface through incorporating a light sensor in a transistor-shaped surface composing a liquid-crystal panel.